Recently, a technique known as OpenFlow has been proposed, see Non-Patent Literatures 1, 2. The OpenFlow comprehends communication as an end-to-end flow and manages path control, recovery from malfunctions, load balancing and optimization from one flow to another. An OpenFlow switch, specified in Non-Patent Literature 2, includes a secure channel over which to communicate with an OpenFlow Controller, and operates in accordance with a flow table an addition to or a rewriting in which is instructed as necessary from the OpenFlow Controller. In the flow table, a set of match conditions (Match Fields) for matching against a packet header, flow statistics information (Counters) and instructions that define the processing contents (Instructions) is defined from one flow to the next. See ‘4.1 Flow Table’ of Non-Patent Literature 2.
On reception of a packet, the OpenFlow switch searches from the flow table an entry having the match condition conforming to the header information of the received packet. See ‘4.3 Match Fields’ of Non-Patent Literature 2. If, as a result of the search, the entry matching the received packet is found, the OpenFlow switch updates the flow statistics information (Counters), at the same time as it executes processing contents stated in an instruction field of the matching entry, such as transmission at an identified port, flooding or dropping. If conversely no entry matching the received packet is found, the OpenFlow switch sends an entry setting request, that is, a request for getting the control information to process the received packet (Packet-In message), to the OpenFlow Controller over the secure channel. The OpenFlow switch receives the flow entry, in which processing contents are stated, and updates the flow table. In this manner, the OpenFlow switch forwards the packet, using the entry, stored in the flow table, as the control information.
It is stated in Example 2 on page 5 of Non-Patent Literature 1 that a virtual network such as VLAN (Virtual Local Area Network) can be provided using a scheme of the OpenFlow described above. It is also stated that the traffic of each user is specified by a port of an OpenFlow switch or by a MAC (Media Access Control) address and that the traffic is tagged with an appropriate VLAN ID by the OpenFlow switch. It is further stated that user authentication is managed by a controller and that the user's location is to be taken into account in tagging the traffic with the VLAN tag.
In Patent Literature 1, there is disclosed a network management system in which a certain user is prevented from seeing the content set by another user or operation data for processing performed by such another user. The network management system according to this Patent Literature includes a resource information repository that prepares and stores virtual network device information objects in terms of the network devices shared or in terms of users sharing the network devices as units. The network management system also includes a virtual resource information accessing means accepting and retrieving a variety of requests made from a terminal to the virtual network devices, and a shared resource information accessing means retrieving the shared network device information objects corresponding to the retrieved objects. It is stated that, by such configuration, a virtual network device that becomes a subset of the shared network devices is virtually constructed for each user and that a certain user may not be see the content set by another user or operation data on the processing performed by such another user.    Patent Literature 1:    JP Patent Kokai Publication No. JP2005-203984A    Non-Patent Literature 1:    Nick McKeown and seven others: “OpenFlow: Enabling Innovation in Campus Networks”, [online], [searched on August 16 Heisei24 (2012)], Internet <URL:http://www.openflow.org/documents/openflow-wp-latest.pdf>    Non-Patent Literature 2:    “OpenFlow Switch Specification”, Version 1.1.0 Implemented (Wire Protocol OxO2), [online], [searched on August 16 Heisei24 (2012)], Internet <URL:https://www.openflow.org/documents/openflow-spec-v1.1.0.pdf>